Pre-clinical treatment of prostate cancer using targeted oncolytic viral therapy

Prostate cancer is the most prevalent non-skin malignancy and the second leading cause of cancer-related mortality in North American men. Current therapies for patients with locally advanced or metastatic prostate cancer are largely palliative and non-curative. Oncolytic viral-therapy provides a new approach to efficiently target and kill cancer cells while sparing normal cells. Vesicular Stomatitis Virus (VSV) is an oncolytic virus, which can infect and kill cells that have defects in their cellular anti-viral interferon (IFN) response. In this study, enhanced IFN-sensitive VSV(AV3) strain was intra-prostatically injected into two different transgenic mouse models (PTEN-/- and TRAMP) and monitored for infectivity, apoptosis, and innate-immune response. Viral spread and load were monitored by bioluminescence and plaque analysis over 96h time period. It was determined that viral spread begins as early as 3-6h post-viral administration and persisted >72h in prostates of tumour-bearing mice compared to control. Plaque assay provided a similar pattern, with much higher concentrations of replicating virus in prostates and metastatic lymph nodes of tumour-bearing mice compared to control. TUNEL staining of paraffin-embedded prostates and enlarged lymph nodes demonstrated VSV(AV3)’s ability to selectively infect and kill malignant cells while sparing normal cells. This tumour-selective cell death was attributed to a disrupted IFN response in the prostates of tumour-bearing transgenic mice. However, evidence of activated IFN response in the enlarged lymph nodes was observed. To augment the safety of future oncolytic viral-therapies alternate targeting strategy based on tumour-specific over-expression of eIF4E was employed. Three different length of 5’UTRs, which require abundant levels of eIF4E for translation, derived from either fibroblast growth factor-2 (FGF-2) or ornithine decarboxylase were inserted downstream of ubiquitin promoter in a lentiviral-plasmid. Expression of each plasmid was tested in vitro using prostate cancer and control cell lines, and in vivo using PTEN-/- and control mice. Immunofluorescence and Western blot analysis determined FGF-2-5’UTR to be most sensitive to eIF4E levels. Results suggested that control of locally advanced and metastatic prostate cancer may be achievable through intra-prostatic injection and amplification of a safe oncolytic virus, such as VSV(AV3). Also, judicious selection of a complex 5’UTR can enhance viral-based targeted-therapies for prostate cancer.Medicine, Faculty ofMedicine, Department ofExperimental Medicine, Division ofGraduat